In the spring of 1974, New Times magazine ran a cover story that listed the 10 dumbest members of Congress. At the top of the list was Virginia Senator William Scott, who’d won the designation for, among other things, dismissing talk during a briefing about missile silos by saying, “I’m not interested in agriculture. I want the military stuff.” The senator, shrewdly concluding that this was not a politically helpful story, promptly called a news conference to deny it. (He retired after one term.)

In September 1987, the presidential campaign of Senator Joe Biden, rocked by charges of plagiarism, was hit by new stories from his law school days. Pressed by a questioner at a gathering in Claremont, New Hampshire, Biden said:

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“I think I probably have a much higher IQ than you do, I suspect. … I won the international moot-court competition … ended up in the top half of my class. I was the outstanding student in the political science department at the end of my year. I graduated with three degrees from undergraduate school and 165 credits — only needed 123 credits. And I would be delighted to sit down and compare my IQ to yours.”

A few days later, after it turned out these boasts were essentially untrue, Biden withdrew from the presidential race.

Can we conclude from these two examples that it’s dangerous for politicians to be defensive about their intelligence? Do these stories suggest that President Donald Trump may be on shaky ground when he offers to “compare IQ tests” with a secretary of state who has refused to deny having called the president a “moron"?

There may be a more useful question to ask: Does it matter how smart the president is? What does a leader’s IQ tell us about how effectively he or she can do the job? In his book “Outliers,” Malcolm Gladwell suggests that it may not matter much beyond a certain threshold. “The relationship between success and IQ works only up to a point,” he writes. “Once someone has reached an IQ of somewhere around 120, having additional IQ points doesn’t seem to translate into any measurable real-world advantage.” A contrary view, at least about presidents, comes from ex-Senator Gary Hart, who argued that “it takes a pretty keen mind, honed by study, travel, experience and exposure to competing ideas, to form good judgment and to know whom to trust on complex substantive issues.” (To which every reader is now shouting, “How keen an intellect does it take not to pose for a picture on a boat called the ‘Monkey Business’ with a young lady perched on your lap?”)

And there’s a more fundamental question to ask: What do we mean by “smart”? For instance, a broad sense of history seems fundamental to a president’s understanding of how the world works; John F. Kennedy’s fascination with the blunders that led leaders into World War I underlined his cautious steps during the Cuban missile crisis and, perhaps, his hesitancy to commit ground troops in Vietnam. But Woodrow Wilson had a distinguished career as an academic specializing in the study of American government, and yet he proved impotent in his effort to get the U.S. Senate to ratify the League of Nations treaty. (His intelligence did not extend to ordinary human decency, either; his blatant racism led to the resegregation of much of the federal government.) Few presidents were as comfortable with the details of public policy as Jimmy Carter, but his understanding of the broader aspects of the job—persuading the public, for example—was far less impressive.

Back in 2006, University of California at Davis psychologist Dean Keith Simonton attempted to assign an IQ to every president using academic performance, writings and other tools. He concluded that John Quincy Adams, Thomas Jefferson and Kennedy were our three "smartest” presidents, while James Monroe, Ulysses S. Grant and Warren Harding were the dimmest. The list is almost designed to trigger arguments; were Franklin Pierce and Millard Fillmore “smarter” than Harry Truman? Was Chester Arthur “smarter” than Theodore Roosevelt? Moreover, no such list can measure aspects that may be much more critical to a president than basic intelligence.

That notion was captured in a famous observation by Justice Oliver Wendell Holmes, who was asked his opinion of President Franklin Roosevelt.

The capacity to understand how the world looks to a potential adversary; to take a step back from the furies of the moment; to know when to fight, when to accommodate, when to yield, are as basic to a president’s ability as any intelligence score. When Ronald Reagan said “my 80 percent friend is not my 20 percent enemy,” he was was asserting a basic rule of effective leadership.

And there are other keys to presidential temperament. When I asked historian David McCullough what traits were most essential for a good president, he did not list intelligence first; he wanted presidents to have had failure or tragedy in their own lives—and also, a sense of humor.

There is, of course, one aspect of intelligence that no president should be without. If we ever had a president who evidenced a deep ignorance of, say, American history, or how the Constitution works, or the interplay of international relations, a president who filtered everything through his or her sense of self-esteem, that president would deserve the epithet the ancient Greeks used to describe one who took no interest in public matters.

As the educator Walter Parker explained the origins of the term several years ago, in an essay arguing for greater civic literacy: “When a person’s behavior became idiotic—concerned myopically with private things and unmindful of common things—then the person was believed to be like a rudderless ship, without consequence save for the danger it posed to others.”

We should not call such a president a moron—we should call him an idiot.